GLONASS Explained

GLONASS is the second-oldest fully-operational GNSS, predating Galileo and BeiDou by decades. This article covers what GLONASS is, its unique design choices (FDMA, orbital inclination), the turbulent history that nearly killed it in the 1990s, and how modern multi-GNSS receivers benefit from including it.

The /learn/how-gps-works pillar covers the underlying GNSS principles; the /learn/gps-vs-gnss article surveys all constellations. This article goes deeper on GLONASS specifically.

The architecture

GLONASS has a satellite constellation of 24 operational satellites (with 4–6 spares typically active) distributed across three orbital planes at ~19,100 km altitude (semi- major axis 25,510 km).

Key parameters:

| Parameter | Value | | ------------------- | -------------------------------------- | | Altitude | ~19,100 km | | Orbital period | ~11 h 16 min | | Inclination | 64.8° (vs GPS's 55°) | | Satellites per plane | 8 | | Operational + spares | 24 + 4–6 spares (varies) | | Reference frame | PZ-90.11 (aligned with ITRF2014 ~1 cm) |

The 64.8° inclination is GLONASS's signature design choice — significantly steeper than GPS's 55°. The steeper inclination means GLONASS satellites pass closer to the poles, providing better satellite geometry at high latitudes. For users in Russia's northern territories (or anywhere above ~60° latitude), GLONASS provides substantially better positioning than GPS alone.

The 11h 16min orbital period is slightly shorter than GPS's ~12h. This means GLONASS satellites complete 17 orbits in 8 sidereal days — a different ground-track repeat pattern than GPS.

FDMA vs CDMA

GLONASS's most distinctive technical feature is its historical use of FDMA (Frequency-Division Multiple Access) for signal differentiation. While GPS uses CDMA (Code-Division Multiple Access, where every satellite broadcasts on the same frequency distinguished by a unique pseudorandom code), GLONASS originally assigned each satellite its own slightly-different frequency channel.

The original GLONASS L1 band: each satellite operates at a frequency in the range 1602–1615 MHz, with channels 0.5625 MHz apart. The receiver tunes to the channel for each tracked satellite. The L2 band uses similar FDMA at 1246– 1257 MHz.

Why FDMA? Soviet electronics in the 1970s were less capable than US silicon, and FDMA simplified the receiver hardware: tuning to a frequency was easier than correlating with a long pseudorandom code. The trade-off: FDMA receivers need more analog hardware (multiple tunable filters) and have inherent receiver-channel biases that must be calibrated.

Modernization to CDMA. GLONASS-K2 satellites (launching since 2014) add CDMA signals on L3 (1202.025 MHz). The modern direction is hybrid: legacy FDMA on L1 and L2 for backwards compatibility, plus new CDMA signals on L3 (and future L1OCM/L1CDMA/L5 bands) that are interoperable with GPS, Galileo, and BeiDou.

For modern multi-GNSS receivers, both FDMA and CDMA GLONASS signals are tracked. The legacy FDMA component requires slightly more receiver complexity, but commodity GNSS chips handle it.

Reference frame and accuracy

GLONASS uses the PZ-90.11 reference frame — Russia's Parametry Zemli (“Earth Parameters”) 1990, with the 2011 realization. PZ-90.11 is aligned with the ITRF (the civilian international reference frame) at the centimetre level, so for multi-GNSS receivers the practical inter-frame bias is small.

Older versions of PZ-90 had larger ITRF offsets (~1 m), causing inter-system biases in early multi-GNSS work. Modern GLONASS-K satellites broadcast PZ-90.11 ephemerides; modern receivers handle the small remaining bias automatically.

Accuracy of standalone GLONASS:

| Service | Accuracy at 95 % | | ---------------- | ---------------- | | Open service | ~5 m horizontal | | With SDCM augmentation | 1–2 m | | Multi-GNSS (GLONASS + GPS + others) | 1–3 m |

SDCM (System for Differential Corrections and Monitoring) is Russia's SBAS — a satellite-based augmentation system providing WAAS-equivalent corrections over Russia and surrounding regions.

A short history

GLONASS development started in 1976 under the Soviet space programme. Key milestones:

• 1976: Programme approved by the Soviet government.
• 1982: First GLONASS satellite launched.
• 1995: Initial Operational Capability declared with 24 satellites. GLONASS operational just months after GPS reached full capability.
• 1995–2001: Post-Soviet collapse. Russia couldn't afford to replace ageing satellites. By 2001, only 7 satellites were operational; positioning was unreliable.
• 2001: President Putin declared GLONASS restoration a strategic priority. Funding restored.
• 2001–2011: Constellation rebuilt with GLONASS-M satellites (improved design, longer lifetime).
• 2011: Full restoration — 24+ satellites operational.
• 2011+: GLONASS-K and GLONASS-K2 satellites add new signals (L3 CDMA), longer operational lifetimes (~10 years vs GLONASS-M's ~7), and better atomic clocks.
• 2020s: Modernization continues; future K2/K3 satellites planned to add full CDMA across all bands.

The 1990s lapse remains a cautionary tale in GNSS infrastructure planning: even mature operational systems can degrade if funding stops. Modern operators (US for GPS, EU for Galileo, China for BeiDou) cite GLONASS's 1990s trajectory as motivation for sustained funding commitments.

GLONASS in modern receivers

Multi-GNSS receivers — including every modern smartphone — track GLONASS alongside GPS by default. The benefits:

• More satellites visible: GPS-only might give 8–12 satellites; GPS + GLONASS gives 15–20.
• Better DOP: especially in challenging environments (urban canyons, high latitudes).
• Faster fix times: more satellites means quicker acquisition.
• Redundancy: if GPS is jammed or has poor geometry, GLONASS continues working.

For users in high-latitude regions (northern Canada, Scandinavia, Russia, Alaska, Antarctica), GLONASS provides materially better coverage than GPS alone because its higher orbital inclination places more satellites near the poles.

For mid-latitude users, GLONASS is a complementary backup and accuracy contributor rather than a primary necessity.

Geopolitical considerations

GLONASS is operated by Russia; its operational priority is Russian sovereign and military use. Civilian access has been freely available since 1994, with explicit commitments to maintain open service published by Roscosmos.

In practice, GLONASS civilian users worldwide rely on Russia to continue operating the constellation. Historical disruptions (the 1990s capability lapse, an April 2014 constellation-wide failure due to a software error) have demonstrated the dependency.

For users requiring positioning independence from any single nation, the practical answer is multi-GNSS: tracking GPS + GLONASS + Galileo + BeiDou ensures that no single operator's disruption produces a positioning outage.

Frequencies and signals

A summary of GLONASS signal frequencies in 2026:

| Signal | Frequency band | Access | Status | | ------------ | -------------------------- | ------ | ----------------------- | | L1OF | 1598.0625–1605.375 MHz | FDMA | Legacy, all satellites | | L2OF | 1242.9375–1248.625 MHz | FDMA | Legacy, all satellites | | L3OC | 1202.025 MHz | CDMA | GLONASS-K, GLONASS-K2 | | L1OC / L1OCM | 1600.995 MHz | CDMA | GLONASS-K2 onward | | L5OCM | 1176.45 MHz | CDMA | Future (interoperable with GPS L5) |

Each FDMA channel pair (L1OF, L2OF) corresponds to a specific satellite slot in the constellation; antipodal satellites in the same orbital plane share frequency channels to conserve spectrum. CDMA signals (L3OC, L1OC, future L5OCM) follow the same approach as GPS, Galileo, and BeiDou — all satellites on the same frequency, distinguished by unique pseudorandom codes.

Modern receivers track FDMA on L1OF/L2OF (where the bulk of the constellation broadcasts) and CDMA on L3OC where available. Multi-frequency civilian users get the same dual- frequency atmospheric-error correction that L1+L5 GPS receivers get.

Practical use cases

Where GLONASS provides specific value above and beyond multi-GNSS in general:

• High-latitude work: Russia, Scandinavia, Alaska, northern Canada, Antarctic stations. The 64.8° inclination means GLONASS satellites pass higher above the horizon than GPS at polar latitudes, providing better DOP and visibility.
• Independence from US GPS: Russian and other users who prefer not to depend on a US-controlled positioning system can use GLONASS as their primary. Modern Russian government vehicles, aviation, and infrastructure rely primarily on GLONASS with GPS as backup.
• Multi-constellation redundancy globally: every user benefits from GLONASS tracking, as the redundancy improves fix reliability and reduces failure modes.

Common misconceptions

“GLONASS is inferior to GPS.” Historically yes — GLONASS lagged GPS in the 1990s and 2000s due to fewer satellites and older hardware. Modern GLONASS (post- 2011 restoration) is comparable to GPS in accuracy. The “inferior” reputation is outdated.

“GLONASS doesn't work outside Russia.” GLONASS is a global system. Satellites broadcast everywhere above the horizon. The constellation is designed for worldwide use; coverage is comparable to GPS globally.

“FDMA is obsolete.” Original GLONASS FDMA is gradually being supplemented by CDMA on modern satellites, but the existing FDMA signals continue and are still tracked by every multi-GNSS receiver. The hybrid FDMA/CDMA approach is GLONASS-specific and not going away.

“You need separate hardware to track GLONASS.” Modern GNSS chips (used in every smartphone) track GPS and GLONASS simultaneously with the same hardware. The receiver firmware handles the FDMA tuning per-satellite automatically.

“GLONASS is the same as GPS, just Russian.” Different technical design choices (FDMA, 64.8° inclination, PZ-90.11 reference frame), different operational philosophy. Functionally similar — both provide ~5 m civilian positioning — but with measurable engineering differences.

“GLONASS accuracy is worse for non-Russian users.” No — the broadcast is the same everywhere. Accuracy is location-dependent (better with more visible satellites, better geometry) but not nationality-dependent. The constellation is designed for worldwide use; Russia has no ability to selectively degrade the signal in other countries the way the US deliberately degraded civilian GPS with Selective Availability before 2000.

“GLONASS doesn't support augmentation.” SDCM (System for Differential Corrections and Monitoring), operated by Russia, provides SBAS-like augmentation for GLONASS and GPS over Russia and surrounding regions. Internationally, IGS (International GNSS Service) provides precise GLONASS satellite products used for PPP work.

“Adding GLONASS makes a receiver more expensive.” For commodity hardware in 2026, the marginal cost is effectively zero — modern GNSS chips (u-blox, Qualcomm, Broadcom, MediaTek) all support GLONASS as standard. The chips are mass-produced in volumes that absorb the multi-constellation cost into the baseline. The receiver firmware adds a few hundred kilobytes for GLONASS handling, trivial on any modern processor.

“GLONASS satellites are decommissioned for political reasons.” Decommissioning happens for technical reasons — atomic-clock failure, solar-panel degradation, end-of-life replacement — not political ones. Russia publishes constellation status openly via the Information and Analysis Center; the available-satellite list is updated daily.